The present invention generally relates to just intonation electronic keyboard instruments, and more particularly to a just intonation electronic keyboard instrument capable of obtaining just intonation notes of a desired key by simple operation of switches.
In the present specification, in order to prevent confusion between the key of music and the key of the keyboard instrument, the key of the keyboard instrument will hereinafter be referred to as the instrument key.
The temperament of just intonation is a frequency series wherein the key-note and each of the notes are in relationships described by frequency ratios which are simple integral ratios, that is, the frequency ratio between two notes in the fifth relationship is 3:2, and the frequency ratio of two notes in the major third relationship is 5:4, for example. In this just intonation, a pure consonance is obtained from the primary triads, and it is possible to realize music having an extremely beautiful sound in the case of unaccompanied chorus and string music. In addition, notes of this kind of temperament is most easily produced by vocal music and string music. For example, the temperament of just intonation is used during a chorus performance wherein pure chords are to be obtained.
During practice of the chorus which uses the temperament of just intonation, it will be effective for teaching purposes if there is a keyboard instrument tuned according to the temperament of just intonation. However, normal keyboard instruments are generally tuned according to the temperament of twelve-temperament.
As described before, the temperament of just intonation is a frequency series wherein the key-note and each of the notes are in relationships described by frequency ratios which are simple integral ratios. Moreover, when modulation is performed to change the key-note, the frequency series of the key-note and each of the notes differ for each of the keys. There are thirty keys including major keys and minor keys. However, because there are six keys in which the scale may be formed by mutually identical keys, it is only necessary to consider twenty-four keys in keyboard instruments. But, an extremely large number of instrument keys will be required to design a keyboard instrument which can freely modulate in the just intonation with respect to these twenty-four keys, and a keyboard instrument having such capabilities could not be realized. Further, in a keyboard instrument which is provided with twelve instrument keys between the C note and the B note and tuned according to a specific key of the just intonation, the key with which the instrument can play became limited because the temperament becomes shifted from the temperament of just intonation when the modulation is performed. Hence, the practical value of this kind of a keyboard instrument was poor.
On the other hand, an instrument tuned according to the equal-temperament cannot obtain perfect chords when compared to an instrument tuned according to the temperament of just intonation. However, the instrument tuned according to the temperament of equal-temperament is capable of obtaining chords which sound substantially natural, and in addition, the modulation operation is simple. For this reason, general electronic keyboard instruments, piano, and the like were conventionally tuned according to the temperament of equal-temperament. However, the chords obtained from the keyboard instruments and the electronic keyboard instruments which are tuned according to the temperament of equal-temperament are not perfect chords as described before, and these instruments are unfit for use in teaching during chorus practice, for example.
As discussed heretofore, it is extremely difficult to realize a keyboard instrument tuned according to the temperament of just intonation which may be effectively used for teaching chorus, as an instrument having the normal construction of a keyboard instrument. However, it is relatively easy to realize such a keyboard instrument as an electronic keyboard instrument. Thus, electronic keyboard instruments capable of easily performing modulation to any key among the twenty-four keys, and also capable of producing sound in accordance with the temperament of just intonation during play in any key among the twenty-four keys, have recently been proposed.
In the conventional just intonation electronic keyboard instrument, the twenty-four keys are displayed by a line of characters such as "C major, . . . , B minor", along the horizontal direction, in an order of the instrument keys acting as the key note according to the order of the instrument keys of the keyboard instrument. Further, tonality switches are provided above the corresponding display characters. The keyboard instrument is set so that just intonation sound of a tonality is obtained, by manipulating these tonality selection switches. However, the tonality display in this conventional keyboard instrument is simply a display in which the tonality is arranged according to the order of the instrument keys. Hence, it was difficult to understand the relationship of the selected tonality. In addition, the operation of the switches was troublesome to perform, because there were so many switches. Therefore, there was a disadvantage in that erroneous operations may be performed, especially in a case where the player is unskilled.